Friday, September 19, 2014

A new Haskell IDE!

Well, that title is click-bait. It's only a proof of concept, so far (-:, sorry!

I wanted to play with Threepenny-GUI since it allowed to do UI the FRP way, without having the troubles of getting a proper UI library to work. And I was going through a period of frustration with EclipseFP, so I thought about something else for a while... It's got the romantic name of HWIDE!

So in fact, this is a very simple integration of CodeMirror and Threepenny-GUI, to be able to edit Haskell sources inside your browser. When you save your buffer, the data is written to disk, and if a cabal file could be found for that source file, a cabal build (in a sandbox) is attempted (with a configure if needed). The output is then parsed by code ripped off BuildWrapper, and the errors/warnings are displayed, so you can click on them and see the offending line in the code.

That's all, really, and even that is not 100% perfect, but it's a start. I could get to play a bit with Events and Behaviors, develop some little widgets. If some FRP experts want to have a look at the code and offer some advice, I'd be all ears!

I probably won't have much time to turn this into the next generation Haskell IDE, but please fork and hack to your heart's content! The repository is at

Happy Haskell Hacking!

Thursday, September 18, 2014

Learning Scala via unit tests

Last month I followed a big data training session, and we used Scala to write algorithms for Spark. I had looked at Scala some years ago but I think at the time the Eclipse support wasn't very good (the pot calling the kettle black, eh?), and it piqued my curiosity again. So I started looking at tutorials, and found Scala Labs. The idea is interesting: you get a project with sources and tests, and you need to make all the tests pass. The source code for both the code to change and the unit tests is heavily documented, and guides you through the language nicely. And seeing the green ticks appear always triggers the proper reward areas of my brain (-:

I had a little issue getting the code to compile using Eclipse, since there's a sbt-launch-0.13.0.jar library at the root of the project, and Eclipse used that as the top library, and it had a weird version of the List class, that wasn't genericized! I removed that jar from the class path and everything worked fine.

I'm not aware of a similar tutorial for Haskell, but that would be a good idea!